One theory of their formation was put forth in 1964 by Lin and Shu. A empirical relationship which defines the luminosity of this object to the amplitude of its rotation curve is given by the Tully-Fisher relation. Hubble first described these objects, suggesting that a central concentration of stars creates a characteristic "bulge." The Triangulum and the Andromeda galaxies are examples of this type and observations from the Spitzer Space Telesc
One theory of their formation was put forth in 1964 by Lin and Shu. A empirical relationship which defines the luminosity of this object to the amplitude of its rotation curve is given by the Tully-Fisher relation. Hubble first described these objects, suggesting that a central concentration of stars creates a characteristic "bulge." The Triangulum and the Andromeda galaxies are examples of this type and observations from the Spitzer Space Telescope suggests, for 10 points, that our own galaxy might be a barred form of this type of galaxy which notably includes arms.
One theory of their formation was put forth in 1964 by Lin and Shu.
{spiral} galaxy [prompt on partial answer]